Apparatus and method to control a linear compressor

ABSTRACT

An apparatus and method that controls the opening/closing of a discharge passage of refrigerant in a linear compressor. The apparatus of the present invention includes a discharge passage opening/closing control unit to control an opening/closing rate of the discharge passage through which high-pressure refrigerant generated by a compression operation of the linear compressor is discharged and moved. The method of the present invention includes sensing an operating state of the linear compressor, comparing the sensed information with a preset value and determining whether the operating state of the linear compressor is abnormal, and controlling the discharge passage of the linear compressor if the operating state of the linear compressor is abnormal.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of Korean Application No. 2002-33820, filed Jun. 17, 2002, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates generally to an apparatus and method to control a linear compressor, and more particularly, to an apparatus and method which controls the opening/closing of a discharge passage that is a passage through which refrigerant discharged from the linear compressor passes.

[0004] 2. Description of the Related Art

[0005] In general, a linear compressor is used in various kinds of refrigerating machines, and refers to a compressor that produces and discharges high-pressure refrigerant through a linear compression process, differently from a rotary compressor.

[0006] Hereinafter, a conventional method of controlling a conventional linear compressor is described with reference to FIGS. 1 and 2.

[0007]FIG. 1 is a sectional view illustrating the conventional linear compressor. FIG. 2 is a block diagram illustrating the conventional linear compressor control method.

[0008] Referring to the FIG. 1, the linear compressor generally comprises a sealed casing 101, a compression chamber that sucks and compresses refrigerant and then discharges the refrigerant, and a drive unit that generates power.

[0009] In more detail, the compression chamber comprises a cylinder 103, a cylinder head 109, and a piston 107. The cylinder 103 is provided with a compression chamber 100. The cylinder head 109 is equipped with suction and discharge valves to guide the suction and discharge of the refrigerant, and is combined with the upper part of the cylinder 103. The piston 107 is provided in the cylinder 103 to perform linear reciprocal movement.

[0010] The drive unit comprises a cylindrically shaped inner core 105, an outer core 104 and a permanent magnet 102 a. The cylindrically shaped inner core 105 is located around the cylinder 103. The outer core 104 is located to be spaced apart from the inner core 105 by a certain distance, and equipped with a coil 106 wound around the inner core 105 to generate a magnetic field when current is applied to the coil 106. The permanent magnet 102 a is located between the inner core 105 and the outer core 104. The permanent magnet 102 a is fixedly supported by a mover 102, and the piston 107 is also fixedly supported by the mover 102. The lower part of the mover 102 is extended to form an extension part 112. The movement of the extension part 112 is sensed by a moving distance sensor 113. That is, the moving distance sensor 113 can sense the moving distance of the piston 107 by sensing the moving distance of the extension part 112.

[0011] Hereinafter, the operation of the linear compressor is described. When a magnetic field is generated around the coil 106 by applying current to the coil 106, a certain amount of magnetic force formed by magnetic fields generated by the current application to the coil 106 and the permanent magnet 102 a acts upon the permanent magnet 102 a. However, since the current applied to the coil 106 is Alternating Current (AC), the directions of the magnetic poles of the magnetic field generated by the coil 106 vary periodically, so the permanent magnet 102 a periodically performs reciprocal movement. In this case, the mover 102 that fixedly supports the permanent magnet 102 a is moved together with the permanent magnet 102 a, and the piston 107 fixedly supported by the mover 102 is reciprocally moved by the mover 102, thus achieving the suction and compression operations of the linear compressor.

[0012] A reference numeral 108 designates a resonant spring that resonates in up and down directions along with the piston 107, and doubles the reciprocal movement of the piston 107. A reference numeral 111 designates a suction muffler that decreases a suction noise when low-pressure refrigerant is sucked to the linear compressor during the suction operation of the linear compressor. A reference numeral 111 a designates a suction pipe that forms a passage through which the low-pressure refrigerant is moved and flows into the linear compressor during the suction operation of the linear compressor. A reference numeral 110 designates a discharge muffler that decreases a discharge noise when high-pressure refrigerant, compressed in a compression chamber during the suction operation of the linear compressor, is discharged outside of the linear compressor. A reference numeral 110 a designates a discharge pipe that forms a discharge passage through which high-pressure refrigerant compressed in the compression chamber during the suction operation of the linear compressor is sucked and moved.

[0013] Next, a conventional method of controlling the conventional linear compressor is described with reference to FIG. 2.

[0014] In general, the method of controlling the conventional linear compressor 200 is carried out by sensing the movement of the piston 107 using the moving distance sensor 113 of FIG. 1, recognizing and evaluating the movement of the piston 107 using a control unit 201, and controlling a power switch 202 using the control unit 201 if excessive movement of the piston 107 occurs. Accordingly, current applied to the coil 106 is cut off and passed by cutting off and passing power supplied to the linear compressor 200, respectively, thereby controlling the operation of the linear compressor. Alternatively, the conventional method of controlling the conventional linear compressor 200 can be carried out by sensing the intensity of current using a current sensor that senses the intensity of the current applied to the linear compressor 200, recognizing and determining the intensity of current using the control unit 201, and cutting off power supplied from a power supply by controlling the power switch 202 if excessive current is applied to the linear compressor 200.

[0015] However, the moving distance of the piston 107 described above does not have a fixed displacement value but a free displacement value. Accordingly, if excessive current is applied to the linear compressor 200, a generated magnetic field is intensified and, therefore, a magnetic field acting on the permanent magnet 102 a is increased, so there occurs a problem in that the piston 107 collides with the cylinder head 109 of the linear compressor. Additionally, the conventional linear compressor control method that was proposed to solve this problem is carried out by sensing the moving distance of the piston or the intensity of the current flowing through the coil, and stopping the operation of the linear compressor by cutting off the current that passes through the coil of the linear compressor if the value of the moving distance or current intensity exceeds a certain value, thereby resulting in the deterioration of reliability on the linear compressor due to the frequent ON/OFF operations of the linear compressor.

SUMMARY OF THE INVENTION

[0016] Accordingly, it is an object of the present invention to provide an apparatus and method to control a linear compressor in accordance with the present invention, which is capable of preventing collisions between a piston and a cylinder head caused by the excessive movement of the piston by controlling the operation of the linear compressor, thereby extending the life-span of the linear compressor, improving reliability on products and preventing the occurrence of abnormalities caused by the frequent ON/OFF operations of the compressor

[0017] Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

[0018] The foregoing and other objects of the present invention are achieved by providing an apparatus to control a linear compressor having a discharge passage opening/closing control unit to control an opening/closing rate of a discharge passage through which high-pressure refrigerant generated by a compression operation of the linear compressor is discharged and moved. Additionally, the discharge passage opening/closing control means preferably includes an automatic control valve that opens or closes the discharge passage, an opening/closing control switch that directs the opening/closing of the automatic control valve, a sensor that senses the operating state of the linear compressor, and a control unit to recognize and evaluate information sensed by the sensor, and controls the automatic control valve or the opening/closing control switch.

[0019] The foregoing and other objects of the present invention are also achieved by providing a method to control a linear compressor, comprising: sensing an operating state of the linear compressor; comparing the sensed information with a preset value and determining whether the operating state of the linear compressor is abnormal; and controlling a discharge passage of the linear compressor if the operating state of the linear compressor is abnormal, wherein the sensing of the operating state of the linear compressor is carried out by sensing a moving distance of a piston in the linear compressor or the intensity of current applied to the linear compressor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] These and other objects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

[0021]FIG. 1 is a sectional view illustrating a conventional linear compressor;

[0022]FIG. 2 is a block diagram that is used to describe a conventional method of controlling the conventional linear compressor;

[0023]FIG. 3 is a view illustrating an apparatus to control a linear compressor according to an embodiment of the present invention;

[0024]FIG. 4 is a view illustrating another apparatus to control a linear compressor according to another embodiment of the present invention;

[0025]FIGS. 5A and 5B are schematic views illustrating the movement of a piston and the direction of force applied to the piston according to the embodiments of FIGS. 3 and 4, respectively; and

[0026]FIG. 6 is a flowchart illustrating a method of controlling a linear compressor according to an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures.

[0028] Hereinafter, the embodiments according to the present invention are described with reference to the accompanying drawings.

[0029]FIG. 3 is a view illustrating an apparatus to control a linear compressor according to an embodiment of the present invention. FIG. 4 is a view illustrating another apparatus to control a linear compressor according to another embodiment of the present invention. FIGS. 5A and 5B are schematic views illustrating the movement of a piston and the direction of force applied to the piston according to an embodiment of the present invention, respectively.

[0030] Referring to FIG. 3, there is illustrated a linear compressor 300. A suction pipe 305 is connected to a side of the linear compressor 300 and forms a passage through which a low-pressure refrigerant is moved during the suction operation of the linear compressor 300. A discharge pipe 303 is connected to another side of the linear compressor 300 and forms a discharge passage through which compressed high-pressure refrigerant is sucked and moved during the suction operation of the linear compressor 300. An automatic control valve 304 is positioned in the discharge pipe 303 and selectively opens and closes the discharge passage formed by the discharge pipe 303. An opening/closing control unit 302 is connected to the automatic control valve 304 and directs the opening/closing of the automatic control valve 304. A moving distance sensor 306 is connected to the linear compressor 300 and senses a moving distance through which the piston of the linear compressor 300 is moved. A control unit 301 recognizes and evaluates information sensed by the opening/closing control switch 302, and commands the opening/closing control unit 302 to direct the automatic control valve 304 to selectively open and close the discharge passage.

[0031] Hereinafter, the above-described embodiment is described in detail.

[0032] When power is supplied to the linear compressor 300 and the linear compressor 300 is operated, the piston in the cylinder of the linear compressor 300 carries out suction and compression operations while regularly moving within a certain range. The low-pressure refrigerant flows into the linear compressor through the suction pipe 305 when the suction operation is carried out, while the high-pressure refrigerant compressed in the linear compressor 300 is discharged from the linear compressor and moved through the discharge pipe 303 when a discharge operation is carried out. When excessive current flows at a moment while carrying out such suction and compression operations, the moving distance of the piston is lengthened. An excessive moving distance of the piston is sensed by the moving distance sensor 306, and sensed information is transmitted to the control unit 301. The control unit 301 recognizes the sensed information, evaluates the operating state of the linear compressor 300 and commands the opening/closing control unit 302 to direct the automatic control valve 304 to block the discharge passage within a certain range corresponding to a distance by which the excessive moving distance of the piston exceeds the normal moving distance of the piston. Accordingly, the opening/closing control unit 302 directs the automatic control valve 304 to block the discharge passage within the certain range, and the automatic control valve 304 blocks the discharge passage within the directed certain range. The discharge passage is not required to be completely blocked. The reason for this is that if the blocking of the discharge passage is performed within the certain range, the discharge passage is blocked to the extent corresponding to the certain range and the movement of the high-pressure refrigerant is interrupted to the extent corresponding to the certain range. Accordingly, it is preferable that the range of the discharge passage able to be blocked by the automatic control valve 304 is preferably designed to be from 0% to 100%. 0% means the complete opening of the discharge passage, and 100% means the complete closing of the discharge passage. The reason why the above-described construction is used is that it is preferable to prevent the linear compressor from suddenly stopping or re-operating due to the fact that the compressor is forced to select complete opening or complete closing depending upon the extent of the abnormal operation of the linear compressor 300, thus allowing smooth control to be implemented.

[0033]FIG. 4 illustrates another embodiment of the present invention, and the same reference numerals are used for the same components as in FIG. 3.

[0034] As illustrated in FIG. 4, a linear compressor 300 employs a current sensor 401 that senses the intensity of the current applied to the linear compressor 300, instead of the moving distance sensor 306, so as to determine the operating state of the linear compressor. Accordingly, the intensity of current is sensed by the current sensor 401, and the sensed information is transmitted to the control unit 301. Thereafter, the control unit 301 accordingly recognizes the intensity of current and determines whether the linear compressor 300 is in an abnormal state. Thereafter, the control unit 301 controls the blocking of the discharge passage to correspond to the extent of the abnormal state. Additionally, it is preferable that an opening/closing rate of the automatic control valve 304 ranges from 0% to 100% to complete the closing of the discharge passage.

[0035] Referring to FIGS. 5A and 5B in conjunction with the embodiment described with reference to FIG. 3, FIG. 5A illustrates a case where, during the normal operation of the linear compressor, high-pressure refrigerant is moved to the head part 503 in a forward direction and discharged by a stable compression operation in which the flow of high-pressure refrigerant in the compression chamber 501 does not exceed a preset displacement of the piston 502. The high-pressure refrigerant moved to the head part 503 is normally moved along the suction pipe through the suction valve (not shown). In contrast, FIG. 5B illustrates a case where, as an abnormal movement, in which the piston 502 is moved an excessive distance more than the preset normal moving distance of the piston 502, the discharge passage is blocked within a certain range corresponding to a distance by which the excessive moving distance of the piston exceeds the normal moving distance of the piston, and, accordingly, the high-pressure refrigerant not discharged from the compression chamber 501 of the linear compressor 300 exerts force in a reverse direction to hinder the piston 502 from moving to the head part 503.

[0036] That is, when the discharge passage formed by the discharge pipe 303 is blocked within the certain range, the flow of the refrigerant discharged from the linear compressor 300 is interrupted by the automatic control valve 304 to an extent corresponding to the certain range during the discharge operation of the linear compressor, and high-pressure refrigerant not discharged from the compression chamber 501 remains in the compression chamber 501. Since the remaining refrigerant applies hydraulic force in the direction opposite to the moving direction of the piston 502 during the compression operation, a collision between the piston 502 and the cylinder head part 503 due to the overload of the linear compressor 300 can be prevented. Of course, it will be easily appreciated that the above-described control method has an effect in which the moving distance of the piston 502 of the linear compressor 300, having a free displacement, approximates the moving distance of a piston having a fixed displacement. Meanwhile, the same effect may be obtained by setting the intensity of current to a certain value instead of setting the preset displacement, and controlling the opening/closing of the automatic control valve 304 according to the set intensity of current.

[0037]FIG. 6 is a flowchart illustrating the method of controlling the linear compressor according to the above embodiment.

[0038] First, referring to FIG. 6, when the linear compressor 300 starts to operate, the moving distance of the piston 502 of the linear compressor 300 is sensed by the moving distance sensor 306 at S601. Thereafter, the control unit 301 compares the value of an actually sensed moving distance with the value of a preset displacement and determines whether the operating state of the linear compressor 300 is abnormal at S602. That is, it is determined whether the moving distance of the piston 502 is greater than the preset displacement. Thereafter, if it is determined that the operating state of the linear compressor 300 is normal on the basis of the determination, the operation in which the moving distance of the piston 502 is continuously sensed and compared with the preset displacement is repeated. In contrast, if it is determined that the operating state of the linear compressor 300 is abnormal on the basis of the information of the determination, that is, the moving distance of the piston 502 is greater than the preset displacement, the moving distance of the piston 502 is continuously sensed and compared with the preset displacement and the opening/closing control unit 302 is commanded to control the automatic control valve 304 at S603. Thereafter, the opening/closing control unit 302 transmits a certain electric signal to the automatic control valve 304 and the automatic control valve 304 is controlled to open or close the discharge passage in response to the electrical signal at S604. The operation of the linear compressor is smoothly carried out through the above-described process. Of course, the operating state of the linear compressor 300 can be sensed by the intensity of current actually applied to the linear compressor 300 at S601. Accordingly, in this case, the preset value of the intensity of current is compared with the intensity of current actually applied to the linear compressor 300, and it is determined whether the operating state of the linear compressor 300 is normal at S602. Of course, the discharge passage is blocked in a range from 0% to 100% to complete the closing of the discharge passage.

[0039] As described above, the apparatus and method to control a linear compressor in accordance with the present invention is capable of preventing collisions between the piston and the cylinder head caused by the excessive movement of the piston by controlling the operation of the linear compressor, thereby extending the lifespan of the linear compressor, improving reliability on products and preventing the occurrence of abnormalities caused by the frequent ON/OFF operations of the compressor.

[0040] Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents. 

What is claimed is:
 1. An apparatus to control a linear compressor, comprising a discharge passage opening/closing control unit to control an opening/closing rate of a discharge passage through which high-pressure refrigerant discharged from the linear compressor is moved.
 2. The apparatus according to claim 1, wherein the discharge passage opening/closing control unit comprises an automatic control valve.
 3. The apparatus according to claim 2, wherein the automatic control valve is installed in a discharge pipe of the linear compressor.
 4. The apparatus according to claim 2, wherein the automatic control valve is regulated to block the discharge passage in a range from 0% to 100%.
 5. The apparatus according to claim 2, wherein the discharge passage opening/closing control unit further comprises a control unit to recognize and evaluate an operating state of the linear compressor and control an opening/closing rate of the automatic control valve.
 6. The apparatus according to claim 2, the discharge passage opening/closing control unit further comprises an opening/closing control unit to direct an opening/closing rate of the automatic control valve in response to an electrical signal.
 7. The apparatus according to claim 6, wherein the discharge passage opening/closing control unit further comprises a control unit to determine the operating state of the linear compressor and control the opening/closing control unit.
 8. The apparatus according to claim 6, wherein the discharge passage opening/closing control unit further comprises a moving distance sensor to sense a moving distance of a piston in the linear compressor and transmit information on the sensed moving distance to the control unit.
 9. The apparatus according to claim 6, wherein the discharge passage opening/closing control unit further comprises a current sensor to sense intensity of current applied to the linear compressor and transmitting information on the sensed intensity of current to the control unit.
 10. A method of controlling a linear compressor, comprising: sensing an operating state of the linear compressor; comparing the sensed information with a preset value and determining whether the operating state of the linear compressor is abnormal; and controlling a discharge passage of the linear compressor if the operating state of the linear compressor is abnormal.
 11. The method according to claim 10, wherein the sensing of the operating state of the linear compressor is carried out by sensing a moving distance of a piston in the linear compressor.
 12. The method according to claim 10, wherein the sensing of the operating state of the linear compressor is carried out by sensing the intensity of current applied to the linear compressor.
 13. The method according to claim 10, wherein the comparing of the sensed information with the preset value is carried out by a control unit.
 14. The method according to claim 13, wherein the controlling of the discharge passage of the linear compressor comprises: allowing the control unit to command an opening/closing control switch so that an automatic control valve is directed to open or close the discharge passage if the operating state of the linear compressor is abnormal; directing the automatic control valve to open or close the discharge passage; and allowing the automatic control valve to control the discharge passage.
 15. The method according to claim 14, wherein the directing of the automatic control valve to open or close the discharge passage is carried out by applying an electrical signal to the automatic control valve.
 16. The method according to claim 10, wherein the discharge passage is blocked within a range from 0% to 100%.
 17. The apparatus according to claim 7, wherein the discharge passage opening/closing control unit further comprises a moving distance sensor to sense a moving distance of a piston in the linear compressor and transmitting information on the sensed moving distance to the control unit.
 18. The apparatus according to claim 7, wherein the discharge passage opening/closing control unit further comprises a current sensor to sense intensity of current applied to the linear compressor and transmit information on the sensed intensity of current to the control unit. 